Method of forming metal tubing

ABSTRACT

A method of forming metal tubing from very thin metal tape, wherein the tape is folded about a non-metallic tubing to convert the same into tubular form; the marginal edge portions of the tape providing tab portions extending radially and in contacting relation, the tab portions being metallically integrated at their outer edges and then folded about the base thereof into contact with the outer surface of the metal tubing; the non-metallic tubing being selectively (1) removed from the formed metal tubing; or (2) retained to form a liner for the metal tubing.

ilnited States atent 1 1 Wa ele 5]March 20 3973 [5 METHOD OF FORMING METAL 2,066,025 12/1936 Zublin et al. ..29/477 TUBING 3,332,138 7/1967 Garner ..29 477.7 x 3,639,970 2/1972 ..29/477.7 X Inventor: Rolf Wagele, Isemhagen, 3,657,809 4/1972 .....29/477.7 x many 3,692,063 9/1972 Wagele ..138/l7l X [73] Assignee: Kabel-und Metallwerke Gutehoft- FOREIGN PATENTS 0R APPLICATIONS mmgshutte Aktiengesellschaft, Hannover, Germany 589,600 5/1930 Germany ..29/473.7

[ Filedi 1971 Primary Examiner-J. Spencer Overholser Assistant Examiner-Richard Bernard Lazarus [2]] Appl' 20l298 Attorney-Philip G. Hilbert [30] Foreign Application Priority Data [57] ABSTRACT Nov.27, 1970 Germany ..P 20 58 379.3 A method of forming metal tubing from very thin metal tape, wherein the tape is folded about a non- 52 us. (:1. ..29/477.7, 29/4733, 29/4739, metallic tubing to convert the same into tubular form; 29 4 0 13 /171 the marginal edge portions of the tape providing tab 51 11m. 01. ..B23k 311/02 portions extending radially and in contacting relation, [58] Field of 29/475 477 477 7 4 0 473 3 the tab portions being metallically integrated at their 29/473] 4739 4741. 138/171 156 outer edges and then folded about the base thereof into contact with the outer surface of the metal tubing; the non-metallic tubing being selectively (1) [56] References Cited removed from the formed metal tubing; or (2) UNlTED STATES PATENTS retained to form a liner for the metal tubing.

1,945,594 2/1934 Chase et al. ..29/477.7 X 8 Claims, 3 Drawing Figures METHOD OF FORMING METAL TUBING BACKGROUND OF THE INVENTION In the copending application Ser. No. 865,097, filed Oct. 9, 1969 and assigned to the same assignee as this application, there is disclosed a method of forming metal tubing derived from very thin metal tape. Such tubing is designed to carry liquid or gaseous, heated or cooled media. In such method the longitudinally extending thin metal tape is folded into tubular form with the marginal edge portions of the tape raised to form a longitudinally extending tab portion with marginal portions in face to face contact.

Further, in such method, the outer edges of the tab portions are metallicaly integrated as by welding to form a fluid proof seam. The metal tubing is then stiffened by applying a metal adherent resin coating to the outer surface thereof. A jacketing of synthetic resin may be applied over the coating.

An object of this invention is to provide an improved method of forming metal tubing from very thin metal tape, wherein the the metal tape is folded about a flexible non-metallic tubing to convert the same to tubular form; the marginal edge portions of the metal tape providing contacting, radial tab portions which are seamed together and folded over into contact with the tubing. The non-metallic tubing provides an improved mandrel and avoids any kinking in the tin metal tape as the same is converted to tubular form.

Another object of this invention is to provide a method of the character described, wherein the nonmetallic tubing may be separated from the formed metal tubing.

A further object of this invention is to provide a method of the character described, wherein the nonmetallic tubing is in integrated relation to the metal tubing as by interposing a layer of adhesive between the tubings; the non-metallic tubing being formed of suitable synthetic resins to afford resistance to corrosive media which may be transported through the tubing.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

DESCRIPTION OF THE DRAWING FIG. l is a side elevational view illustrating the method of the instant invention;

FIG. 2 is a transverse section taken on the line 2-2 of FIG. ll; and

FIG. 3 is an enlarged transverse sectional view showing tubing made by the method ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Essentially, the method of making metal tubing in accordance with the instant invention comprises folding a thin metal tape to tubular form about a flexible mandrel of non-metallic material such as synthetic resin, or the like. The folded tape is ofa width such as to provide tab portions derived from the marginal edge portions of the tape, which are in face to face relation and extend radially of the tubing.

The tab portions are integrated at their outer edges as by welding or the like; folded over into contact with the outer surface of the metal tubing. A coating of metal adherent synthetic resin is then applied to the outer surface of the metal tubing, and may be followed by a jacketing of synthetic resin.

The flexible mandrel may be removed from the finished tubing of selected length; or, may be integrated with the metal tubing by interposing a layer of adhesive between the tubings.

Thus, as shown in FIG. 1, the method of the instant invention may be carried out by the apparatus set forth. Metal tape M is drawn from a supply reel, not shown; such tape being of aluminum, copper, stainless steel, or the like, with a thickness not exceeding 0.3 mm. The tape M is moved along a forming table T where it is converted to tubular form.

To this end there is provided a mandrel 40, preferably formed of a synthetic resin in tubular form. Mandrel 40 is coaxially related to known folding means 21 which effects the conversion of the tape M to tubular form.

As the tape Ml has a width greater then the circumference of the tubing 11 being formed; marginal portions of the tape indicated at 22 are disposed in face to face relation and extend radially with respect to the tubing. Preferably, the tab forming portions 22 are trimmed as by trimming means 23, to provide tabs 15, thus making outer edges 16 coextensive; the trimmed portions 22A being suitably removed.

The freshly trimmed edges 16 of tabs 15 are oxide free, which is particularly important when tape M is aluminum, since such edges 16 now pass in proper alignment to an integrating zone 25 where welding means 26. located in suitably spaced relation to edges 16, produces a longitudinally extending weldment 17.

The welding operation takes place under a protective u atmosphere of argon or the like, in a manner known in the art.

The resultant tab seam 15 is then folded over from its radial disposition, by suitable folding die 27, against the outer surface of tubing 11. A metal adherent synthetic resin coating 18 is applied over tubing 11 by an extruder 28. Resin coating 18 is of the type disclosed in U.S. Pat. Nos. 2,987,501 and 3,027,346, and essentially are copolymers of polyethylene and selected monomers.

A jacketing coating 19 may then be applied over coating 18, as by an extruder 29. Coating 19 may be of polyethylene, polyvinyl chloride or the like. The tubing thus formed is drawn off by suitable draw-off means, no shown. 7

The tubing 40 in addition to providing mandrel means for forming metal tubing 11, may also be integrated with tubing 11, as by applying a coating of adhesive 42 to the outer surface of tubing 40, as by coating die 41. Such adhesives may be thermosetting so that upon reaching zone 25, the welding means 26 will provide the heat for setting coating 42. Also, the heat of extruders 28, 29 may also insure the bonding action of adhesive coating 42.

The tubing 40 is preferably of a synthetic resin such as polyamide (Nylon) or polytetrafluorethylene (Teflon) with a wall thickness of the order of from 1.0 to 3.0 mm. for tubings ranging in diameters of 10 to mm. The adhesive 42 is thus selected in accordance with the nature of the resin forming tubing 40. Accordingly, the finished, composite tubing, FIG. 3; is adequate to carry corrosive media in liquid or gaseous form Alternatively, the tubing mandrel 40 may be separated from the formed tubing 11, in which case the adhesive coating 42 is omitted. In this case, tubing 11 is formed in selected lengths, thereby allowing for removal of tubing 40 therefrom.

Iclaim:

1. The method of forming metal tubing from a metal tape having a thickness not exceeding 0.30 mm. comprising moving a non-metallic tubing in a longitudinal path, continuously folding said tape about the outer surface of said non-metallic tubing and bringing longitudinal marginal portions of said tape into face to face relation to form a longitudinally extending radial tab, metallically integrating the longitudinal exposed edges only of said tab to form a fluid proof seam while leaving said tab of uniform thickness from the base to the outer edge thereof, folding said tab at the base thereof into contact with outer surface portions of said folded tape, and applying a synthetic resin coating in bonding relation to the outer surface of said folded tape.

2. The method as in claim 1 and further including the step of removing the non-metallic tubing from the metal tubing formed by the folded metal tape.

3. The method as in claim 1 and further including the step of applying an adhesive coating between the opposed surface portions of said non-metallic tubing and said folded metal tape, whereby to bond said nonmetallic tubing to the metal tubing.

4. The method as in claim 3, wherein said non-metallic tubing is formed of polyamide.

5. The method as in claim 3, wherein said non-metallic tubing is formed of polytetrafluorethylene.

6. The method as in claim 3, wherein the exposed edges of said tab are welded together, said adhesive coating being thermoresponsive and set to a bonding condition by the welding step.

7. The method as in claim 1, wherein said synthetic resin coating is a monomer-polyethylene copolymer and further including the step of applying a jacketing layer of synthetic resin to the outer surface of said synthetic resin coating.

8. The method as in claim 1, wherein said non-metallic tubing has a wall thickness of from 1.0 to 3.0 mm. 

1. The method of forming metal tubing from a metal tape having a thickness not exceeding 0.30 mm. comprising moving a nOn-metallic tubing in a longitudinal path, continuously folding said tape about the outer surface of said non-metallic tubing and bringing longitudinal marginal portions of said tape into face to face relation to form a longitudinally extending radial tab, metallically integrating the longitudinal exposed edges only of said tab to form a fluid proof seam while leaving said tab of uniform thickness from the base to the outer edge thereof, folding said tab at the base thereof into contact with outer surface portions of said folded tape, and applying a synthetic resin coating in bonding relation to the outer surface of said folded tape.
 2. The method as in claim 1 and further including the step of removing the non-metallic tubing from the metal tubing formed by the folded metal tape.
 3. The method as in claim 1 and further including the step of applying an adhesive coating between the opposed surface portions of said non-metallic tubing and said folded metal tape, whereby to bond said non-metallic tubing to the metal tubing.
 4. The method as in claim 3, wherein said non-metallic tubing is formed of polyamide.
 5. The method as in claim 3, wherein said non-metallic tubing is formed of polytetrafluorethylene.
 6. The method as in claim 3, wherein the exposed edges of said tab are welded together, said adhesive coating being thermoresponsive and set to a bonding condition by the welding step.
 7. The method as in claim 1, wherein said synthetic resin coating is a monomer-polyethylene copolymer and further including the step of applying a jacketing layer of synthetic resin to the outer surface of said synthetic resin coating.
 8. The method as in claim 1, wherein said non-metallic tubing has a wall thickness of from 1.0 to 3.0 mm. 